Caloplaca chrysophthalma. This is an extreme, and slightly misunderstood rarity. I was told it grew on an elm in Hugh Town Bay churchyard on St Mary's, Isles of Scilly by the late, and very great Peter James. I twitched it. It is tiny, but I got the attached photo. For a time it was thought that the similar Caloplaca sorediella that occurs, amongst other places on dead Crithmum maritimum on Bardsey Island was it. Shown here is a photograph of the true species. It consists of bright orange soralia on an immersed, inconspicuous grey thallus. It is always on trees and is confined to the Isles of Scilly. Caloplaca sorediella has a more conspicuous grey thallus, and consists of bright orange, delimited soralia arising from an areolate white or grey thallus. Not easy! It has confused some pretty eminent lichenologists.